Precision cleaning and drying systems typically utilize a wide variety of cleaning solutions including various solvents, detergents, or other aqueous mixtures. These systems operate to clean and dry various devices or parts such as medical devices, optical instruments, wafers, PC boards, hybrid circuits, disk drive components, precision mechanical or electromechanical components, or the like. In the precision cleaning industry in particular, there exists a need for an efficient cleaning system generally having a high tank turnover rate.
Ultrasonic systems for processing and cleaning parts within a tank are generally known. In a typical prior art ultrasonic system, the tank contains a cleaning solution and the parts to be cleaned are introduced therein. Ultrasonic energy is applied to the tank, and the ultrasonic vibrations generate pressure gradients within the cleaning solution, forming minute cavitation bubbles. These cavitations implode against a surface of the part to be cleaned releasing tremendous energy thereby dislodging contaminants.
In prior art systems, the ultrasonic energy is turned off while the solution within the tank is refreshed. For example, new or filtered solution is pumped into bottom of the tank, while the solution within the tank containing the contaminants overflows one or more sides out of the tank, to be filtered and reused or discarded. It is necessary to apply ultrasonic energy separately from refreshing the tank in these systems because the turbulence associated with a high rate of tank refreshing flow disrupts the ultrasonic wave pattern that produces the ultrasonic cavitations. In prior art ultrasonic systems, mixing of contaminants within the tank with the refreshed solution still occurs such that the contaminants are eliminated slowly in a logarithmic manner over time. Logarithmic elimination of all contaminants theoretically takes an infinite amount of time, greatly reducing the overall turnover clean up rate.
One prior art ultrasonic system, described in U.S. Pat. No. 6,181,052, attempted to create laminar flow within the tank by including at least two baffles at the bottom of the tank. The purpose of the baffles was to reduce the velocity of the incoming cleaning solution, equalize the pressure of the clean solution, and introduce the solution in the bottom of the tank with equal spatial distribution. However, these baffles as described have two serious shortcomings to achieve the desired results. First the upper baffle was welded into place within the tank, or mounted within the tank such that the mounting bracket interferes with uniform flow up along the sidewalls of the tank, which introduces a counter-current within the tank causing turbulent mixing which again slows down the elimination of contaminants from the tank and the overall turnover rate. Secondly, the large open area of this baffle plate, a minimum of 45% open, prevents uniform upward flow from developing by failing to develop uniform pressure behind the second baffle.